The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An air conditioning system mounted on an automobile has a function of providing a pleasant environment to a passenger in the automobile even in a change of weather or driving conditions. In the air conditioning system of the automobile, blown air moves along an air duct which is a transfer path of the air and is blown into the automobile through an air vent which is connected to one end of the air duct.
The air duct for the automotive air conditioning system is generally manufactured by blow-molding the polyethylene resin. However, a solid type air duct manufactured by molding polyethylene has become an impediment to reduction in weight of the automobile due to the large density.
In the solid type air duct, a condensation phenomenon of moisture is generated due to poor insulation and cooling and heating efficiency of the automobile is reduced, and thus, emission quantity of carbon dioxide is increased and fuel efficiency of the automobile is reduced. As a result, non-woven fabric is attached to an outer part of the solid type air duct to reduce noise while improving insulation. However, a problem in the weight is still present and there is a limitation of adding a manufacturing process.
In order to solve the problem, research in which a foaming body which is foamed with a foaming agent to be light and has excellent insulation for application to the air duct has been continued. However, the foaming air duct may not obtain desired strength due to limitation of a kind of resin configuring the foaming body, and thus, it is difficult to manufacture an air duct having good mechanical properties and there is a limitation that the surface quality of the finally-produced air duct is bad.
In Korea Patent Publication No. 10-2015-0143199, a molded article foamed by including a polyethylene resin having a crystallization temperature of 112 to 150° C., a low density polyethylene resin, an inorganic filler, and an olefin-based polymer is described. A polypropylene resin having a crystallization temperature of 112 to 150° C. measured by a differential scanning calorimeter (DSC) is included in a base to minimize a phenomenon in which foaming cells are exploded on the surface when manufacturing the molded article through rapid surface elevation. However, we have discovered that since deterioration of properties may occur due to compatibility between the polypropylene resin and the inorganic filler, there is a disadvantage in that an olefin-based polymer as a compatibilizer needs to be included as a required component.